With the recent change in the Japanese eating habits into Western-style ones to take high-calorie and high-cholesterol foods and drinks, which is based on the improvement in the living standard in Japan, and with the recent increase in the aged population of Japan, cases of hyperlipemia and arteriosclerotic disorders resulting from hyperlipemia are greatly increasing with bringing about one social problem in Japan. The conventional chemotherapy for cases of hyperlipemia and arteriosclerosis is essentially to lower their blood-lipid levels that participate in the disorders, but is not targeted to the focuses themselves of arteriosclerosis to cure them.
Acyl coenzyme A cholesterol acyltransferase (ACAT) is an enzyme to catalyze the transfer of cholesterol into cholesterol esters, while playing an important role in the metabolism of cholesterol and the absorption thereof through digestive systems. It is believed that the inhibition of such an ACAT enzyme that may catalyze the esterification of free cholesterol in epithelial cells in small intestines brings about the inhibition of the cholesterol absorption through intestinal tubes, while the inhibition of the formation of cholesterol esters in the liver based on the ACAT inhibition brings about the inhibition of the VLDL (very low-density lipoprotein) secretion into blood, thereby resulting in the decrease in the blood cholesterol. Many known ACAT inhibitors are expected to act on ACAT in small intestines and the liver as anti-hyperlipemic agents thereby to lower blood cholesterol.
For example, as ACAT inhibitors, U.S. Pat. No. 4,716,175 discloses 2,2-dimethyl-N-(2,4,6-trimethoxyphenyl)dodecanamide, and European Patent 372,445 discloses N'-(2,4-difluorophenyl)-N-[5-(4,5-diphenyl-1H-imidazol-2-ylthio)pentyl]-N- heptylurea. However, many known ACAT inhibitors have heretofore been specifically directed to the decrease in blood cholesterol as anti-hyperlipemic agents, and administered to patients in large amounts in order to express their effects. Therefore, in the clinical examination stage using them, many patients have experienced various side effects such as bleeding from the intestinal tubes, intestinal disorders, diarrhea and liver disorders, which have made it difficult to develop the clinical use of ACAT inhibitors.
WO92/09582 discloses compounds having a certain substituent at the 2-position of the imidazole skeleton; and EP-A 477,778 discloses compounds having certain substituents at the 4- and 5-positions of the imidazole skeleton. For example, disclosed are 5-[2-(2-(4-fluorophenyl)ethyl)-3-(1-methyl-1H-imidazol-2-yl)-2H-benzopyran -6-yl]oxy-2,2-dimethyl-N-(2,6-diisopropylphenyl)pentanamide (see WO92/09582), N-(2,6-diisopropylphenyl)-2-(tetradecylthio)acetamide (see JP 92-500533, WO92/09572), N-butyl-N'-[2-(3-(5-ethyl-4-phenyl-1-yl)propoxy)-6-methylphenyl]urea (see EP 477,778), and N-[5-(4,5-diphenyl-1H-imidazo-2-ylthio)pentyl]-N-heptyl-2-enzoxazolamine (see WO93/23392); and it is disclosed that these compounds have ACAT inhibiting activities. However, the chemical structures of these compounds are quite different from those of the compounds of the present invention.
3-(benzothiazol-2-ylthio)-N-(phenyl)propanamide, 3-(benzothiazol-2-ylthio)-N-(phenyl)ethanamide and 3-(benzothiazol-2-ylthio)-N-(p-chlorophenyl)ethanamide is reported in J. Chem. Eng. Data, 27, 207 (1982) and 3-(benzoxazol-2-ylthio)-N-(phenyl)propanamide is reported in Fungitsidy, Ed. Melnikov, N. N. Izd. Fan Uzb. SSR: Tashkent, USSR, 82-88 (1980).